Light-emitting diode lighting device which improves line regulation

Abstract

An LED lighting device includes a luminescent device driven by a rectified AC voltage, a current detecting circuit, a current regulating circuit, and a duty cycle detecting circuit. The current regulating circuit is configured to provide a regulating current so that the current flowing through the luminescent device does not exceed the regulating current. The current detecting circuit is configured to monitor the value of the regulating current, and the duty cycle detecting circuit is configured to monitor the duty cycle of the regulating current. The present invention can improve the overall line regulation of the LED lighting device when the rectified AC voltage somehow fluctuates between its upper bound and lower bound.

What is claimed is: 
     
       1. A light-emitting diode (LED) lighting device which improves line regulation, comprising:
 a current detecting circuit configured to monitor a first current and provide a feedback voltage associated with the first current; 
 a duty cycle detecting circuit configured to monitor a duty cycle of the first current and provide a control signal associated with the duty cycle of the first current; and 
 a current regulating circuit configured to:
 provide the first current for regulating a second current so that a value of the second current does not exceed a value of the first current, wherein the second current flows through a luminescent device driven by a rectified alternative-current (AC) voltage; and 
 adjust the value of the first current according to the feedback voltage and the control signal; the current regulating circuit comprising:
 a first switch, comprising:
 a first end coupled to the luminescent device; 
 a second end coupled to the current detecting circuit; and 
 a control end coupled to a first switching signal; and 
 
 a first comparator, comprising:
 a first input end coupled to a reference voltage; 
 a second input end coupled to the current detecting circuit for receiving the feedback voltage; and 
 an output end coupled to the control end of the first switch and configured to output the first switching signal according to a relationship between the reference voltage and the feedback voltage. 
 
 
 
 
     
     
       2. The LED lighting device of  claim 1 , wherein the current regulating circuit further comprises a reference voltage generator configured to provide the reference voltage according to the control signal. 
     
     
       3. The LED lighting device of  claim 1 , wherein the duty cycle detecting circuit comprises:
 a second switch, comprising:
 a first end coupled to a bias voltage; 
 a second end for providing the control signal; and 
 a control end coupled to a second switching signal; 
 
 a third switch, comprising:
 a first end coupled to a ground voltage; 
 a second end coupled to the second end of the second switch; and 
 a control end coupled to the second switching signal; and 
 
 a second comparator, comprising:
 a first input end coupled to a threshold voltage; 
 a second input end coupled to the current detecting circuit for receiving the feedback voltage; and 
 an output end coupled to the control end of the second switch and the control end of the third switch, and configured to output the second switching signal according to a relationship between the threshold voltage and the feedback voltage. 
 
 
     
     
       4. The LED lighting device of  claim 3 , wherein the duty cycle detecting circuit further comprises a resistor which includes:
 a first end coupled to the second end of the second switch and the second end of the third switch; and 
 a second end coupled to the current regulating circuit. 
 
     
     
       5. The LED lighting device of  claim 1 , wherein the current detecting circuit comprises a detecting resistor coupled between the current regulating circuit and a ground voltage. 
     
     
       6. The LED lighting device of  claim 1 , wherein the current regulating circuit and the duty cycle detecting circuit are formed in a chip which includes:
 a first pin coupled to the luminescent device; 
 a second pin coupled to a ground voltage; and 
 a third pin coupled to the current detecting circuit. 
 
     
     
       7. The LED lighting device of  claim 6 , wherein the chip further includes a fourth pin coupled to the rectified AC voltage. 
     
     
       8. The LED lighting device of  claim 1 , further comprising a charge storage unit coupled between the duty cycle detecting circuit and a ground voltage. 
     
     
       9. The LED lighting device of  claim 8 , wherein the current regulating circuit and the duty cycle detecting circuit are formed in a chip which includes:
 a first pin coupled to the luminescent device; 
 a second pin coupled to the ground voltage; 
 a third pin coupled to the current detecting circuit; 
 a fourth pin coupled to the charge storage unit. 
 
     
     
       10. The LED lighting device of  claim 9 , wherein the chip further includes a fifth pin coupled to the rectified AC voltage. 
     
     
       11. The LED lighting device of  claim 1 , further comprising a power supply circuit for providing the rectified AC voltage. 
     
     
       12. A light-emitting diode (LED) lighting device which improves line regulation, comprising:
 a current detecting circuit configured to monitor a first current and provide a feedback voltage associated with the first current; 
 a duty cycle detecting circuit configured to monitor a duty cycle of the first current and provide a control signal associated with the duty cycle of the first current, and comprising:
 a first switch, comprising:
 a first end coupled to a bias voltage; 
 a second end for providing the control signal; and 
 a control end coupled to a switching signal; 
 
 a second switch, comprising:
 a first end coupled to a ground voltage; 
 a second end coupled to the second end of the first switch; and 
 a control end coupled to the switching signal; and 
 
 a comparator, comprising:
 a first input end coupled to a threshold voltage; 
 a second input end coupled to the current detecting circuit for receiving the feedback voltage; and 
 an output end coupled to the control end of the first switch and the control end of the second switch, and configured to output the switching signal according to a relationship between the threshold voltage and the feedback voltage; and 
 
 
 a current regulating circuit configured to:
 provide the first current for regulating a second current so that a value of the second current does not exceed a value of the first current, wherein the second current flows through a luminescent device driven by a rectified alternative-current (AC) voltage; and 
 adjust the value of the first current according to the feedback voltage and the control signal. 
 
 
     
     
       13. The LED lighting device of  claim 12 , wherein the duty cycle detecting circuit further comprises a resistor which includes:
 a first end coupled to the second end of the first switch and the second end of the second switch; and 
 a second end coupled to the current regulating circuit. 
 
     
     
       14. The LED lighting device of  claim 12 , wherein the current detecting circuit comprises a detecting resistor coupled between the current regulating circuit and the ground voltage. 
     
     
       15. The LED lighting device of  claim 12 , wherein the current regulating circuit and the duty cycle detecting circuit are formed in a chip which includes:
 a first pin coupled to the luminescent device; 
 a second pin coupled to the ground voltage; and 
 a third pin coupled to the current detecting circuit. 
 
     
     
       16. The LED lighting device of  claim 15 , wherein the chip further includes a fourth pin coupled to the rectified AC voltage. 
     
     
       17. The LED lighting device of  claim 12 , further comprising a charge storage unit coupled between the duty cycle detecting circuit and the ground voltage. 
     
     
       18. The LED lighting device of  claim 17 , wherein the current regulating circuit and the duty cycle detecting circuit are formed in a chip which includes:
 a first pin coupled to the luminescent device; 
 a second pin coupled to the ground voltage; 
 a third pin coupled to the current detecting circuit; 
 a fourth pin coupled to the charge storage unit. 
 
     
     
       19. The LED lighting device of  claim 18 , wherein the chip further includes a fifth pin coupled to the rectified AC voltage. 
     
     
       20. The LED lighting device of  claim 12 , further comprising a power supply circuit for providing the rectified AC voltage.